viernes, 28 de abril de 2017

Excercise, Macronutrients and immunology part III Protein and Amino Acids

As the debate about fat and carbohydrate rages on, I think everybody can agree that protein is essential. Even the moderately active individual needs to have a higher than recommended protein intake. This is the final article that summarises the latest evidence on the role of the macronutrients in exercise and immunology (click here and here to read the previous two articles). The article will not look at protein as a whole but on the amino acids that have been researched the most in terms of their effect on the immune system post exercise. These amino acids are the branched chain amino acids (BCAA) and glutamine. Remember that if you want to read about this topic in more detail please consult the Exercise and Immunology review1.

The branched chain amino acids (leucine, isoleucine and valine) are probably one of the most popular sports nutrition supplements, especially among people who regularly lift weights. During long bouts of exercise the BCAAs are utilised by the working muscles and this causes the plasma concentration of BCAA to fall. Apart from being used for energy, the metabolism of BCAA produces nitrogen which is used for glutamine synthesis. During exercise, a reduction in plasma glutamine has been observed which has been linked to exercise-induced immunodepression. 
It was suggested that BCAA intake could indirectly influence immune response by increasing glutamine synthesis. As we all know, just because something sounds good in theory doesn’t mean it will work in practice. Despite the fact that supplementing with BCAA during exercise did indeed increase both plasma and muscle concentrations, this did not lead to an increase in plasma glutamine. 
There is some evidence that chronic supplementation of BCAA can prevent the decrease in plasma glutamine and other markers of exercise-induced immunodepression.
BCAA, in particular leucine, may have a direct effect on the immune system through their effect on the mTor signalling pathway. mTor stimulates muscle protein synthesis and activates cytokine and antibody production. Again, somewhat predictably, the evidence is lacking and what data there is indicates that BCAA has a greater involvement in muscle protein synthesis as opposed to immune function.

The authors conclude that there is some evidence that BCAA can reduce exercise-induced immunodepression but not enough to recommend its use for athletes in the context of immune function.

It is worth remembering that the BCAA use the same transporter during digestion and that when they are taken in large amounts (for example as a supplement) the amino acid that is in the highest concentration (usually leucine) is absorbed at the expense of the other two2. Therefore, I would suggest that BCAA supplementation in general may not be as advantageous as diet rich in high quality proteins.

Moving away from BCAA as a precursor to glutamine and to glutamine itself. Glutamine is the most abundant amino acid in the body and was originally thought to be non-essential. However, during times of stress to the body the requirement increases so it has been renamed conditionally essential. It is synthesised, stored and released mainly in the skeletal muscle, and among the numerous cells that utilise it are the immune cells, such as, macrophages, neutrophils and lymphocytes. As mentioned before, prolonged exercise results in a decrease in plasma glutamine concentration, a decrease in immune function is simultaneously observed.

As with BCAA supplementation, the rationale is sound but disappointingly, the results from studies of glutamine supplementation do not live up to the expectation.
In conclusion, while there are some encouraging signs that BCAA and glutamine may influence immune function, the evidence is not currently strong enough to promote the supplementation of either. As I stated before, what is essential is that you have a diet rich in high quality protein. 
Before even considering supplementation of any kind you should always evaluate the quality of your diet and address any issues. If you would like to know more about our sports nutrition packages please contact us on 

1.Berman S et al. (2017) Immunonutrition and Exercise Consensus Statement. Exercise and Immunology Review: Vol 23
2. Gropper, S.S & Smith, (2013) J.L Advanced Nutrition and Human Metabolism 6th Edition. Wadsworth Cengage Learning